In the field of high energy primary cells, the thionyl chloride cell system appears very attractive for its high open circuit potentials, high theoretical energy density, broad operating temperature ranges and storeability. Both calcium and lithium cells have been studied. The main incentive for using calcium in place of the more popular lithium is that calcium anodes have higher melting temperatures than lithium anodes. The disparity between the melting points of these two metals is of special interest since 839.degree. C. required to melt calcium would not likely be reached by any internally driven cell condition. This precludes the likelihood of difficulties traceable to a molten anode leading to thermal run aways often seen in lithium-thionyl chloride cells.
However, carbon cathode capacities tend to be lower for calcium based cells than for analogous lithium cells due to formation of a glassy calcium chloride deposit rather than the crystalline lithium chloride deposit normally formed in lithium based cells.